contestada

As you stand by the side of the road, a car approaches you at a constant speed, sounding its horn, and you hear a frequency of 76 Hz. After the car goes by, you hear a frequency of 65 Hz. What is the speed of the car? The speed of sound in the air is 343 m/s.

Respuesta :

Answer:

26.8 m/s

Explanation:

[tex]v[/tex]  = constant speed of the car

[tex]V[/tex]  = speed of sound = 343 m/s

[tex]f[/tex] = actual frequency of the horn

[tex]f_{app}[/tex] = frequency heard as the car approach = 76 Hz

frequency heard as the car approach is given as

[tex]f_{app}=\frac{vf}{V - v}[/tex]

[tex]76 =\frac{vf}{343 - v}[/tex]                               eq-1

[tex]f_{rec}[/tex] = frequency heard as the car recedes = 65 Hz

frequency heard as the car goes away is given as

[tex]f_{rec}=\frac{vf}{V + v}[/tex]

[tex]65 =\frac{vf}{343 + v}[/tex]                                  eq-2

dividing eq-1 by eq-2

[tex]\frac{76}{65}=\frac{343+v}{343-v}[/tex]

[tex]v[/tex] = 26.8 m/s

Otras preguntas